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United States Patent |
5,139,552
|
Yoshizawa
,   et al.
|
August 18, 1992
|
Apparatus for bending and tempering sheet glass
Abstract
A glass sheet such as an automobile window glass sheet is bent to shape and
tempered at one stage by a sheet glass bending and tempering apparatus.
The sheet glass bending and tempering apparatus has solid contact members
for pressing a glass sheet, which has been heated nearly to its softening
point, to a desired shape and depriving the glass sheet of heat to cool
the glass sheet quickly, the solid contact means having a contact surface
for contacting the glass sheet and depriving the glass heat of heat
therethrough. The contact surface has a plurality of grooves defined
therein, and a plurality of air outlet ports defined in each of the
grooves, for applying cooling air to the glass sheet, and a plurality of
air inlet ports defined in each of the grooves, for drawing the air
applied to the glass sheet. When the opposite surfaces of the glass sheet
are pressed by the solid contact members, the pressure is temporarily
reduced and then increased again to cool the glass sheet. The peripheral
edge of the glass sheet, which requires a high degree of shaping accuracy,
is cooled quickly by the solid contact members, and the central region of
the glass sheet, which requires high optical properties, is cooled quickly
by air jets.
Inventors:
|
Yoshizawa; Hideo (Osaka, JP);
Kasugai; Toru (Osaka, JP)
|
Assignee:
|
Nippon Sheet Glass Co., Ltd. (Osaka, JP)
|
Appl. No.:
|
622731 |
Filed:
|
December 5, 1990 |
Foreign Application Priority Data
| Dec 05, 1989[JP] | 1-316277 |
| Dec 08, 1989[JP] | 1-320203 |
| Dec 19, 1989[JP] | 1-328949 |
Current U.S. Class: |
65/273; 65/103; 65/114; 65/348; 65/351 |
Intern'l Class: |
C03B 027/04 |
Field of Search: |
65/348,351,273,287,103,106,114,289
|
References Cited
U.S. Patent Documents
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|
3249415 | May., 1966 | McMaster et al. | 65/160.
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3293021 | Dec., 1966 | Stilley et al. | 65/111.
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3365286 | Jan., 1968 | Nedelec | 65/114.
|
3529947 | Sep., 1970 | Frank | 65/104.
|
3554724 | Jan., 1971 | Ritter, Jr. et al. | 65/107.
|
3573022 | Mar., 1971 | Frank | 65/104.
|
3582304 | Jun., 1971 | Bognar | 65/105.
|
3595636 | Jul., 1971 | Posney | 65/287.
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3634059 | Jan., 1972 | Miller | 65/273.
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3676098 | Jul., 1972 | Hall | 65/106.
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3744985 | Jul., 1973 | Peternel | 65/104.
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3827872 | Aug., 1974 | Augustin et al. | 65/114.
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3955955 | May., 1976 | Melling | 65/104.
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4043782 | Aug., 1977 | Bamford et al. | 65/104.
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4071344 | Jan., 1978 | Blausey, Jr. | 65/29.
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4071345 | Jan., 1978 | Werner et al. | 65/273.
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4305746 | Dec., 1981 | Hagedorn et al. | 65/106.
|
4396410 | Aug., 1983 | Hagedorn et al. | 65/106.
|
4488846 | Dec., 1984 | Halberschmidt et al. | 414/152.
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4615931 | Oct., 1986 | Matsuyoshi et al. | 428/174.
|
4749399 | Jun., 1988 | Yamada | 65/348.
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4756735 | Jul., 1988 | Cathers et al. | 65/106.
|
4767439 | Aug., 1988 | Reunamaki | 65/351.
|
4826522 | May., 1989 | d'Iribarne et al. | 65/115.
|
4840657 | Jun., 1989 | Orain | 65/107.
|
4973344 | Nov., 1990 | Rahrig et al. | 65/288.
|
Foreign Patent Documents |
799907 | Nov., 1968 | CA.
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0053551 | Jun., 1982 | EP.
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0143691A3 | Jun., 1985 | EP.
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0277074A1 | Aug., 1988 | EP.
| |
0361263A2 | Apr., 1990 | EP.
| |
0404676A1 | Dec., 1990 | EP.
| |
2336513 | Jul., 1973 | DE.
| |
3344083C1 | Oct., 1984 | DE.
| |
1580305 | Sep., 1969 | FR.
| |
2164455 | Dec., 1971 | FR.
| |
2112115 | Jun., 1972 | FR.
| |
59-213635 | Dec., 1984 | JP.
| |
61-17775 | May., 1986 | JP.
| |
61-28611 | Jul., 1986 | JP.
| |
62-18488 | Apr., 1987 | JP.
| |
62-40298 | Aug., 1987 | JP.
| |
63-43324 | Aug., 1988 | JP.
| |
63-260833 | Oct., 1988 | JP.
| |
63-63493 | Dec., 1988 | JP.
| |
WO89/07581 | Aug., 1989 | WO.
| |
782502 | Sep., 1957 | GB.
| |
2011377 | Jul., 1979 | GB.
| |
2162170A | Jan., 1986 | GB.
| |
2166133A | Apr., 1986 | GB.
| |
2185974A | Aug., 1987 | GB.
| |
2188045A | Sep., 1987 | GB.
| |
Other References
English abstract for Japanese Patent Publication No. 59-213635.
English abstract for Japanese Patent Publication No. 62-18488.
English abstract for Japanese Patent Publication No. 62-40298.
English abstract for Japanese Patent Publication No. 63-43324.
English abstract for French Patent No. 2.164.455.
|
Primary Examiner: Lindsay; Robert L.
Attorney, Agent or Firm: Merchant, Gould, Smith, Edell, Welter & Schmidt
Claims
We claim:
1. An apparatus for shaping and tempering a glass sheet, comprising:
solid contact means for pressing a glass sheet, which has been heated
nearly to a softening point thereof, to a desired shape and absorbing heat
from the glass sheet to cool the glass sheet quickly, said solid contact
means having a contact surface for contacting the glass sheet and
absorbing heat from the glass sheet therethrough; and
said contact surface having a plurality of grooves defined therein, and a
plurality of air outlet port means defined in each of said grooves, for
applying cooling air to the glass sheet, and a plurality of air inlet port
means defined in each of said grooves, for drawing the air applied to the
glass sheet.
2. An apparatus according to claim 1, wherein said grooves extend parallel
to each other.
3. An apparatus according to claim 1, wherein said grooves extend across
each other.
4. An apparatus according to claim 1, wherein each of said grooves has a
width ranging from 2 mm to 15 mm and a depth ranging from 1 mm to 6 mm.
5. An apparatus according to claim 1, wherein said air outlet port means
and said air inlet port means in each of said grooves are alternately
arranged.
6. An apparatus according to claim 1, further including a mesh-like
metallic sheet covering said contact surface and said grooves.
7. An apparatus according to claim 6, further including a surface member
covering said mesh-like metallic sheet.
8. An apparatus according to claim 1, further including a surface member
covering said contact surface and said grooves.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of and an apparatus for bending
and tempering a sheet of glass, especially for use as an automobile window
glass sheet, at one stage.
2. Description of the Relevant Art
One general process for tempering a sheet of glass employs air jets which
are applied to the glass sheet over its surface. Other glass sheet
tempering methods include a process in which a sheet of glass to be
tempered is submerged in a liquid, and a process in which a solid contact
member made of a material of good thermal conductivity, such as boron
nitride, stainless steel, or the like, is held against a sheet of glass to
deprive the contacted glass surface of heat.
Japanese Patent Publication No. 62(1987)-40298, for example, discloses an
air jet process. According to the disclosed process, a sheet of glass to
be tempered is not constrained after it is bent until it is rapidly
cooled, and hence the glass sheet tends to be deformed. When a glass sheet
is bent to a greater curvature, it is more liable to get deformed.
The solid member contact method is disclosed in Japanese Patent
Publications Nos. 62(1987)-18488 and 63(1988)-43324 and Japanese Laid-Open
Patent Publications Nos. 59(1984)-213635 and 63(1988)-260833, for example.
According to the method disclosed in Japanese Patent Publication No.
62(1987)-18488, a metallic cooling plate for contacting a sheet of glass
is divided or has a groove to reduce any thermal expansion thereof due to
a temperature rise. The process disclosed in Japanese Patent Publication
No. 63(1988)-43324 employs a main cooling device for cooling a sheet of
glass with air jets after the glass sheet is preliminarily cooled by
contact with a solid contact member.
The method shown in Japanese Patent Publication No. 62(1987)-18488 is
disadvantageous in that the glass sheet cannot uniformly be cooled, a
drawback which is inherent with the solid member contact process.
According to the process shown in Japanese Patent Publication No.
63(1988)-43324, since the glass sheet is cooled in two steps, the overall
apparatus required to carry out the method is large in size, and when the
glass sheet is bent, it tends to be deformed while being fed after it is
preliminarily cooled.
In order to deprive a glass sheet of heat quickly in the solid member
contact method, it is necessary to press the solid contact member against
the glass sheet relatively strongly. When the glass sheet which has been
heated nearly to its softening point is cooled, the glass sheet shrinks to
a certain degree. Therefore, if the glass sheet remains to be gripped
under pressure by the solid contact member, tensile stresses are developed
in the glass sheet owing to the shrinkage caused when the glass sheet is
cooled. If the tensile stresses exceed the mechanical strength of the
glass sheet, then the glass sheet will crack.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of and an
apparatus for bending and tempering a sheet of glass so that the bent and
tempered sheet of glass is of uniform mechanical strength, shaped with
high accuracy, and has reduced optical defects.
According to the present invention, there is provided an apparatus for
shaping and tempering a glass sheet, comprising solid contact means for
pressing a glass sheet, which has been heated nearly to a softening point
thereof, to a desired shape and depriving the glass sheet of heat to cool
the glass sheet quickly, the solid contact means having a contact surface
for contacting the glass sheet and depriving the glass heat of heat
therethrough, the contact surface having a plurality of grooves defined
therein, and a plurality of air outlet ports defined in each of the
grooves, for applying cooling air to the glass sheet, and a plurality of
air inlet ports defined in each of the grooves, for drawing the air
applied to the glass sheet. The glass sheet is cooled by both the solid
contact means and the cooling air, and hence is cooled uniformly over its
entire surface.
When the opposite surfaces of the heated glass sheet are pressed by the
solid contact members, the pressure is temporarily reduced and then
increased again to cool the glass sheet. Because the pressure with which
the glass sheet is pressed by the solid contact means is temporarily
lowered, tensile stresses produced in the glass sheet due to shrinkage
thereof when the glass sheet is cooled are released.
The peripheral edge of the glass sheet, which requires a high degree of
shaping accuracy, is cooled quickly by the solid contact members, and the
central region of the glass sheet, which requires high optical properties,
is cooled quickly by air jets.
The above and further objects, details and advantages of the present
invention will become apparent from the following detailed description of
preferred embodiments thereof, when read in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front elevational view of a sheet glass bending and tempering
apparatus according to a first embodiment of the present invention;
FIG. 2 is an enlarged fragmentary perspective view of a contact layer of a
shaping mold member as a solid contact member;
FIGS. 3a through 3g are schematic views showing a progressive process of
operation of the sheet glass bending and tempering apparatus shown in FIG.
1;
FIG. 4 is an enlarged fragmentary perspective view of a solid contact
member according to a modification;
FIG. 5 is a fragmentary perspective view showing the manner in which a
suspended sheet of glass is bent and cooled;
FIG. 6 is a front elevational view of a sheet glass bending and tempering
apparatus according to a second embodiment of the present invention;
FIGS. 7a through 7e are schematic views showing a progressive process of
operation of the sheet glass bending and tempering apparatus shown in FIG.
6;
FIG. 8 is a front elevational view of a sheet glass bending and tempering
apparatus according to a third embodiment of the present invention;
FIG. 9 is a plan view taken along line IX--IX of FIG. 8;
FIG. 10 is a cross-sectional view of a means for cooling a peripheral edge
of a sheet of glass;
FIGS. 11 through 13 are cross-sectional view of other means for cooling a
peripheral edge of a sheet of glass;
FIG. 14 is a schematic view of a sheet glass bending and tempering
apparatus which has separate means for shaping and cooling a central
region of a sheet of glass; and
FIG. 15 is a plan view taken along line XV--XV of FIG. 14.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Like or corresponding parts are denoted by like or corresponding parts
throughout views.
A sheet glass bending and tempering apparatus according to a first
embodiment of the present invention will be described below with reference
to FIGS. 1 through 5.
The sheet glass bending and tempering apparatus, generally denoted at 1, is
disposed adjacent to and downstream of a heating furnace 2 which houses
feed rolls 3 for feeding a glass sheet G. The glass sheet G is heated
nearly to its softening point while it is being fed in the heating furnace
2. The heated glass sheet G is attracted by a flat suction pad 4 under
suction, and delivered from the heating furnace 2 into the sheet glass
bending and tempering apparatus 1. The sheet glass bending and tempering
apparatus 1 is followed by feed rolls 5 which feed a bent and tempered
glass sheet G to a next process. The bent and tempered glass sheet G is
transferred from the sheet glass bending and tempering apparatus 1 onto
the feed rolls 5 by a suction assembly 6.
The glass sheet bending and tempering apparatus 1 includes a bending mold
device having an upper convex mold member 7 and a lower concave mold
member 8. The upper convex mold member 7 is vertically movably supported
on a frame 9 by a cylinder unit 10 mounted on an upper member of the frame
9. The lower concave mold member 8 is fixedly mounted on a floor below the
upper convex mold member 7. However, the lower concave mold member 8 may
be vertically movably mounted on the floor, and may be combined with a
ring mold (not shown).
Each of the convex and concave mold members 7, 8 serves as a solid contact
member in the sold member contact process. The convex and concave mold
members 7, 8 are pressed against a glass sheet G to shape the same to a
bent configuration and also to deprive the contacted class sheet surfaces
of heat, thereby tempering the glass sheet G.
As shown in FIG. 2, each of the convex and concave mold members 7, 8 has an
integral contact surface 11 for contacting the glass sheet G, the contact
surface 11 having a plurality of parallel grooves 12 defined therein. The
contact surface 11 also has alternate air outlet ports 13 and air inlet
ports 14 defined therein and opening into each of the grooves 12. The air
outlet ports 13 are connected to a source of air under pressure by
suitable means such as pipes. The contact surface 11 is fully covered with
a mesh-like metallic sheet 15 and a surface member 16.
The grooves 12 may be defined in the contact surface 11 such that they
intersect as shown in FIG. 4. In FIG. 4, one set of parallel grooves 12
and another set of parallel grooves 12 extend across each other at a given
angle in a grid-like pattern.
As shown in FIG. 2, the contact surface 11 has a plurality of parallel
narrow raised ridges or lands defined between the grooves 12, for contact
with the glass sheet G. Each of these ridges or lands has a width X
ranging from 0.5 mm to 10 mm. Each of the grooves 12 has a width Y ranging
from 2 mm to 15 mm, and a depth Z ranging from 1 mm to 6 mm. These
dimensions of the contact surface 11 are effective to cool the glass sheet
6 uniformly while preventing the glass sheet G from being deformed. It is
preferable that air jets ejected from the air outlet ports 13 be applied
obliquely and uniformly to the surface of the glass sheet G, so that the
glass sheet G will uniformly be cooled without any localized excessive
cooling. The air which is applied from the air outlet ports 13 to the
glass sheet G and is heated thereby is drawn into the air inlet ports 14.
Therefore, the glass sheet G can effectively be cooled within a short
period of time.
The mesh-like metallic sheet 15 should preferably have a mesh size ranging
from 100 to 400 mesh in terms of the number of openings per square inch.
If the mesh size were smaller than 100 mesh, then the mesh mark would be
left on the glass sheet surface, and if the mesh size were greater than
400 mesh, the metallic sheet 15 would block the flow of air. The metallic
sheet 15 and the surface member 16 may not be superposed, but are more
effective when superposed. The surface member 16 should preferably be a
woven or felt layer of glass fibers, ceramic fibers, carbon fibers,
metallic fibers, aramid fibers, or the like, the layer or felt having a
thickness ranging from 0.3 mm to 0.5 mm.
Operation of the bending and tempering apparatus 1 will be described below
with reference to FIGS. 3a through 3g.
As shown in FIG. 3a, a heated glass sheet G in the heating furnace 2 is
attracted by the flat suction pad 4 under suction. The glass sheet G is
then transferred from the heating furnace 2 into a position between the
convex and concave mold members 7, 8 of the bending and tempering
apparatus 1 as shown in FIG. 3b. The glass sheet G is placed on the
concave mold member 8 as shown in FIG. 3c. Thereafter, as shown in FIG.
3d, the glass sheet G is pressed to a bent shape by and between the convex
and concave mold members 7, 8, while at the same time the contacted
surfaces of the glass sheet G are deprived of heat, so that the glass
sheet G is quickly cooled. At the same time, cooling air jets are applied
from the air outlet ports 13 to the surfaces of the glass sheet G, and the
heated air is drawn into the air inlet ports 14. The glass sheet G is now
tempered. Thereafter, the convex and concave mold members 7, 8 are moved
away from each other as shown in FIG. 3e. The suction assembly 6 is then
inserted between the convex and concave members 7, 8 as shown in FIG. 3f,
after which the glass sheet G is attracted by the suction assembly 6 and
transferred from between the convex and concave mold members 7, 8 onto the
feed rolls 5 as shown in FIG. 3g.
While the glass sheet G is horizontally placed between the upper and lower
mold members in FIG. 1, the glass sheet G may be vertically suspended by
tongues 17 and bent and cooled while being held in the vertically
suspended condition.
FIG. 6 shows a sheet glass bending and tempering apparatus according to a
second embodiment of the present invention. Those parts in FIG. 6 which
are identical to those in FIG. 1 are designated by identical reference
numerals.
The sheet glass bending and tempering apparatus, generally denoted at 101,
has an upper convex mold member 107 and a lower concave mold member 108. A
clamp unit 111 is disposed on one side of the concave mold member 108. The
clamp unit 111 has a clamp 112 vertically movable by a cylinder unit 113.
When the clamp 112 is lowered, it presses a central region of a glass
sheet G at one side thereof against the concave mold member 108. The
convex mold member 107 has a recess 114 defined in one side thereof for
receiving the clamp 112 when the glass sheet G is shaped between the mold
members 107, 108 and clamped down against the concave mold member 108 by
the clamp 112.
The convex and concave mold members 107, 108 have respective contact
surface layers 115 extending fully over their confronting surfaces. Each
of the contact surface layers 115 comprises a woven or felt layer.
However, each contact surface layer 115 may have the same structure as
shown in FIG. 2 or 4, so that the surfaces of the glass sheet G can be
cooled by both the contact surface layers 115 and air jets.
Operation of the glass sheet bending and tempering apparatus 101 will be
described below with reference to FIGS. 7a through 7e.
As shown in FIG. 7a, a glass sheet G in the heating furnace 2 is attracted
by the flat suction pad 4 under suction. Then, the glass sheet G is
transferred into a position between the convex and concave mold members
107, 108 as shown in FIG. 7b, and placed on the concave mold member 108 as
shown in FIG. 7c. Thereafter, as shown in FIG. 7d, the glass sheet G is
pressed to a bent shape by and between the convex and concave mold members
107, 108, while at the same time the contacted surfaces of the glass sheet
G are deprived of heat, so that the glass sheet G is cooled quickly and
hence tempered. At this time, the glass sheet G is clamped down against
the concave mold member 108 by the clamp 112 of the clamp unit 111.
Upon elapse of 2 to 10 seconds after the glass sheet G has started to be
pressed, the pressure applied to the glass sheet G is lowered. The period
of time consumed after the glass sheet G has started to be pressed until
the pressure applied to the glass sheet G is lowered, should be selected
such that tensile stresses produced in the glass sheet G upon cooling
thereof will not exceed the mechanical strength of the glass sheet G.
When the pressure is lowered as described above, the glass sheet G slides
over the surface of the concave mold member 108 under the tensile stresses
as shown in FIG. 7e, whereupon the tensile stresses are released. At this
time, the glass sheet G is prevented from being positionally displaced by
the clamp unit 111 which holds a side portion of the glass sheet G on the
concave mold member 108. Thereafter, the pressure is increased again. If
the glass sheet G is suspended by the tongues 17 shown in FIG. 5 and bent
in the vertically suspended condition, then the glass sheet G is held in
position by the tongues 17. In the second embodiment, the glass sheet G is
both bent and cooled quickly. However, the glass sheet G may not be bent
but may only be cooled quickly.
FIGS. 8 and 9 show a sheet glass bending and tempering apparatus 201
according to a third embodiment of the present invention.
As shown in FIG. 8, the sheet glass bending and tempering apparatus 201 has
an upper convex mold member 209 and a lower concave mold member 210. A
glass sheet G heated nearly to its softening point in the heating furnace
2 is transferred by feed rollers 203 onto rollers 204 in the sheet glass
bending and tempering apparatus 201 which is disposed downstream of the
heating furnace 2. After the glass sheet G is bent to shape and cooled
quickly by the convex and concave mold members 209, 210, the glass sheet G
is delivered out of the apparatus 201 by feed rollers 5.
As shown in FIG. 9, each of the feed rollers 203 comprises a core 203a
curved to a shape corresponding to a bent configuration to be assumed by
the glass sheet G, and a heat-resistant sleeve 203b rotatably mounted on
the core 203a. The feed rollers 203 therefore serve as preliminary shaping
rollers for shaping the glass sheet G while feeding the same with the
sleeves 203b rotating around the respective cores 203a.
The sheet glass bending and tempering apparatus 201 also includes a means
206 for quickly cooling a peripheral edge of the glass sheet G with solid
contact members, and a means 207 for quickly cooling a central region of
the glass sheet G with cooling air.
As shown in FIG. 10, the means 206 for quickly cooling glass sheet
peripheral edges comprises a pair of upper and lower metallic ring mold
members 208 each covered, at its confronting surface, with a surface
member 208a for contacting the glass sheet G. The surface member 208a is
identical in construction to the surface member 16 shown in FIG. 2. Each
of the ring mold members 208 has a portion for contacting the peripheral
edge of the glass sheet G, the portion having a width W1 ranging from 5 to
20 mm for ordinary automobile window glass sheets.
The means 207 for quickly cooling a central glass sheet region is composed
of the convex and concave mold members 209, 210, which also serve as a
means for bending the glass sheet G. The convex and concave mold members
209, 210 are hollow and connected to a source of air under pressure. Each
of the convex and concave mold members 209, 210 has an air outlet ports
211 defined in its shaping or contact surface. The convex mold member 209
is vertically movable with respect to a frame 213 by a cylinder unit 212,
and the concave mold member 210 is vertically movable with respect to a
floor by a cylinder unit 214. The concave mold member 210 has a plurality
of recesses 215 for receiving some of the feed rollers 214 when the
concave mold member 210 is elevated.
The sheet glass bending and tempering apparatus 201 operates as follows:
With the convex and concave mold members 209, 210 spaced from each other,
a heated glass sheet G is preliminarily shaped by the feed rollers 203 and
transferred onto the feed rollers 204 in the apparatus 201. Then, the
peripheral edge of the glass sheet G is gripped by the ring mold members
208, and the feed rollers 204 are lowered as shown in FIG. 8. The convex
mold member 209 is lowered and the concave mold member 210 is elevated to
bend a central region of the glass sheet G therebetween. Simultaneously,
the peripheral edge of the glass sheet G is bent by the ring mold members
208.
Thereafter, while the peripheral edge of the glass sheet G is being held by
the ring mold members 208, the convex and concave mold members 209, 210
are spaced from the surfaces of the glass sheet G, and air jets are
ejected from the air outlet ports 211 to cool the central region of the
glass sheet G quickly. The air jets should preferably be applied to the
glass sheet G while the glass sheet G gripped by the ring molds 208 is
horizontally moved back and forth, so that the glass sheet G can uniformly
be cooled.
At the same time that the central region of the glass sheet G is cooled
quickly by air jets ejected from the air outlet ports 211, the peripheral
edge of the glass sheet G is also cooled quickly by the ring molds 208. To
cool the peripheral edge of the glass sheet G quickly, the ring molds 208
are pressed against the peripheral edge of the glass sheet G under a
pressure in the range of from 500 to 1000 kgf, which is higher than the
pressure applied to press the glass sheet G to bent shape, so that the
peripheral edge of the glass sheet G is forcibly deprived of heat.
FIGS. 11 through 13 show other means 306, 406, 506, respectively, for
quickly cooling the peripheral edge of a glass sheet. Each of these means
306, 406, 506 quickly cools the peripheral edge of a glass sheet with
solid contact members and air jets.
In FIG. 11, each of ring mold members 308 comprises a hollow pipe of
rectangular cross section which is connected to a source of air under
pressure. The ring mold members 308 have nozzle holes 308 for ejecting air
jets to the peripheral edge of a glass sheet G through mesh members 317 of
stainless steel wires and cloth members 318 of stainless steel fibers. For
a greater cooling effect, the surfaces of the ring mold members 308 which
confront the glass sheet G should preferably have guide grooves 319 for
guiding air jets.
In FIG. 12, each of hollow ring mold members 408 have nozzle holes 416
defined in side walls thereof, and guide plates 420 for directing air jets
from the nozzle holes 416 toward the surfaces of a glass sheet G. Since
air jets are not directly applied to the glass sheet G, high optical
properties are imparted to the peripheral edge of the glass sheet G. The
surfaces of the ring molds 408 which face the glass sheet G are covered
with respective surface members 408a. The ring molds 408 are held against
the glass sheet G over an interval or width W1 ranging from 5 to 20 mm.
The guide plates 420 are spaced from the confronting side walls of the
respective ring molds 408 by a distance W2 ranging from 5 to 10 mm, since
if the distance W2 were too large, the peripheral edge of the glass sheet
G would not sufficiently be cooled.
In FIG. 13, cooling plates 521 as solid contact members and pipes 422
having nozzle holes 416 for ejecting air jets are separate from each
other. Air jets ejected from the nozzle holes 416 are directed toward the
glass sheet G by guide plates 420.
FIGS. 14 and 15 show a sheet glass bending and tempering apparatus
according to another embodiment of the present invention.
In the embodiment shown in FIGS. 8 and 9, the means 207 for quickly cooling
a central glass region is composed of the convex and concave mold members
209, 210, which also serve as a means for bending the glass sheet G. In
FIGS. 14 and 15, however, the convex and concave mold members 209, 210 are
used exclusively for bending a glass sheet G, and the central region of
the glass sheet G is cooled by a pair of toothed cooling devices 223
disposed upwardly and downwardly, respectively, of the glass sheet G, the
cooling devices 223 being movable toward and away from each other. In the
embodiment shown in FIGS. 14 and 15, the central region of a glass sheet G
can be bent to shape and cooled quickly in different successive steps at
one stage.
While a glass sheet is bent to shape in a horizontal condition in the
embodiment shown in FIGS. 14 and 15, the glass sheet may be bent in a
vertical condition.
With the present invention, as described above, a sheet of glass is
tempered without deformations, and air flows on the surfaces of the glass
sheet which are contacted by the mold members when the glass sheet is
sandwiched between the mold members. Therefore, the glass sheet is
uniformly cooled, and hence tempered without mechanical strength
irregularities.
The glass sheet is prevented from being broken while it is being cooled
because the pressure applied to the glass sheet to shape the same is
lowered before tensile stresses produced in the glass sheet upon cooling
thereof exceed the mechanical strength of the glass sheet. The accuracy
with which the glass sheet is bent to shape is high since a portion of the
glass sheet is fixed in position when the pressure applied to the glass
sheet is lowered.
The peripheral edge of the glass sheet is cooled by solid contact members
or a combination of solid contact members and air jets, and the central
region of the glass sheet is cooled quickly by air jets. With such a
cooling arrangement, the glass sheet is bent and tempered with high
shaping accuracy and reduced optical defects.
Although there have been described what are at present considered to be the
preferred embodiments of the present invention, it will be understood that
the invention may be embodied in other specific forms without departing
from the essential characteristics thereof. The present embodiments are
therefore to be considered in all aspects as illustrative, and not
restrictive. The scope of the invention is indicated by the appended
claims rather than by the foregoing description.
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